LabMed

Primary Hypoaldosteronism

At a Glance

Presentation with symptoms of mild volume depletion, such as decreased blood pressure and postural hypotension together with hyperkalemia and hyponatremia, are suggestive of primary hypoaldosteronism.

This disorder results from injury or genetic defects in adrenal cells producing aldosterone. Hypoaldosteronism can occur as part of the presentation of Addison’s disease, resulting from destruction of both adrenal glands or due to selective injury to cells producing aldosterone. Addison’s disease can be a medical emergency due to deficiency of cortisol, as well as of aldosterone and other mineralocorticoids. It can result from autoimmune disease, granulomatous disease, such as tuberculosis and fungal infections, neoplastic infiltration, hemorrhage related to anticoagulants or meningococcal infection, hemochromatosis, or amyloidosis. Addison’s disease may present with hyperpigmentation.

Selective loss of aldosterone producing cells can occur after prolonged heparin therapy or after hypotensive episodes during surgery or critical illness. Many patients with critical illness and with AIDS have impaired aldosterone production despite increased renin. Primary hypoaldosteronism may also result from inherited deficiencies of the 21-hydroxylase. This enzyme deficiency occurs in about 1 out of 10,000 newborns and can present in newborns as congenital adrenal hyperplasia.

The disorder may present in girls as ambiguous genitalia and in boys as precocious puberty. Adult women may present with hirsutism or symptoms similar to the polycystic ovary syndrome. Deficiency of aldosterone, in some cases, can present as salt wasting and hypotension in newborns.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Serum electrolyte measurements will usually show increased potassium and decreased sodium, chloride, and bicarbonate with a mild acidosis. Urine will have a relatively low potassium concentration. Plasma aldosterone is decreased, and plasma renin is usually increased. Primary hypoaldosteronism is distinguished from secondary hypoaldosteronism by the plasma renin activity, which usually is increased or normal in primary hypoaldosteronism and decreased in secondary hypoaldosteronism.

Serum cortisol measurements help identify whether function of the adrenal cortex is preserved. If an inherited deficiency of the 21-steroid hydroxylase enzyme is suspected, a serum profile of steroids hormones, including 17-hydroxyprogesterone and aldosterone, should be performed. 17-hydroxyprogesterone, progesterone, pregnenolone, and 17-hydroxypregnenolone, as well as some androgens, are increased. Aldosterone, deoxycorticosterone, 11-deoxycortisol, and cortisol are decreased.(Table 1)

Table 1.

Serum potassium

Plasma aldosterone

Plasma renin

High

Low

High or normal

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

A number of factors can lead to factitiously high measured values of potassium. Excessive tourniquet time or fist clenching during specimen collection can lead to increases in serum potassium. Hemolysis of specimens and prolonged storage of serum on the clot can lead to increases in potassium. Increases in platelet count increases serum potassium because of release of potassium from platelets during specimen clotting.

Aldosterone production is inhibited by a number of medications, such as angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers, renin inhibitors, nonsteroidal anti-inflammatory drugs, and beta blockers. Aldosterone production is also suppressed by volume overload and sodium loading.

What Lab Results Are Confirmatory?

Response of the hypotension and electrolyte disturbance to fludrocortisones treatment combined with increased salt intake helps to confirm diagnosis.

What Factors, if Any, Might Affect the Confirmatory Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

Electrolyte measurements can be affected by many factors, including fluid intake, kidney function, intravenous fluid administration, stress, and other factors affecting release of antidiuretic hormone. Cortisol levels are subject to a diurnal rhythm and respond to stress. Cortisol values may be either suppressed or increased by exogenous corticosteroids, depending on cross-reactivity with the cortisol assay.

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